He did not go to university, but became an articled clerk with a firms of solicitors in Manchester, and later studied for the bar, and was a pupil in Gordon Hewart's chambers.

After the war, Merriman was made a King's Counsel (KC) in 1919, and appointed Recorder of Wigan in 1920.

In 1929, he represented Zionist organisations in front of the Shaw Commission, appointed to investigate the Palestine riots.

[1] He left Parliament in 1933, when he was appointed as President of the Probate, Divorce and Admiralty Division of the High Court, when he was also sworn of the Privy Council.

In 1949, Merriman was considered for appointment as a lord of appeal in ordinary, but ultimately passed over in favour of Sir Cyril Radcliffe.